It is often desired to compact a material for the purpose of reducing the material to a desired density. Examples of applications where compaction is desired include construction sites to prevent further natural settling of the ground, landfill sites where it is desired to compact the landfill waste into as small a volume as possible, and blacktop roads and parking lots, where it is desired to prevent further settling of the blacktop, and hence prevent future cracking of the road or parking lot.
The amount of compaction of these materials must be monitored by some means to determine when the material is compressed to a desired density. In the past, various methods for determining an amount of compaction have been employed. For example, direct measurements of material density may be performed at either random or predetermined locations. The measurements may be made by removing core samples of the material for density measurements, or by sand or water displacement devices. Alternatively, the measurements may be made by some means which does not disturb the material, such as by nuclear gauges, electromagnetic measurement devices, and the like.
The above methods for determining the density of the material being compacted only provide indications of density at the sample locations chosen for testing. In addition, the above methods require additional time and work by the persons performing the tests. This additional time and work increases costs and reduces efficiency of the compaction process. Furthermore, the methods discussed above which disturb portions of the compacted area are not desirable in some situations, e.g., when compacting blacktop in a parking lot, as the disturbance of the material adversely affects the finished product.
In U.S. Pat. No. 5,471,391, Gudat et al. discloses a method and apparatus whereby compacting machines monitor their position with respect to the terrain being compacted, and indicate on a display a number of times portions of the terrain have been passed over by the compactor. In this system, a determination is made as to how many passes would be needed to complete compaction. When the desired number of passes is made over an area, compaction is considered to be complete.
The method and apparatus disclosed by Gudat et al. works well to provide an estimated evaluation of the degree of compaction of a site. However, the method does not measure or determine directly the amount of compaction performed. Therefore, some accuracy is sacrificed to provide the advantage of a real time indication of when compaction is considered to be complete.
The above discussion indicates that many methods have been devised to measure or estimate the amount of compaction that has been performed on a material. However, it is desired to devise a method which can directly measure an amount of compaction, in real time, of the entire volume of material being compacted without intrusively disturbing the material.
The present invention is directed to overcoming one or more of the problems as set forth above.